Cutting instruments

ABSTRACT

A process for making a cutting instrument includes cutting a blank from a plate or strip of Type 60 Nitinol, having a thickness of between 0.005″-0.500″ using an abrasive waterjet, wire electron discharge machining or laser cutting, and grinding top and bottom surfaces of the blank by rotating a grinder having cubic boron nitride or diamond abrasive particles on a cutting surface of said grinder against the knife blank at a surface speed of about 5000 to 7000 surface feet per minute and grinding to a depth of about 0.001 to 0.005 inches per pass to remove material along the blade surface. The surface of the blade is polished to a surface finish smoother than 20 microinches RMS using Turkish emery abrasive grinding/polishing materials on a buffing wheel driven by a high power motor. The blade is then finish polished to a mirror-like luster of 2 microinches RMS or less using a fine diamond buffing compound and a buffing wheel running at about 3000 RPM. An edge is ground into the polished blade blank using an Arkansas stone grinder.

This invention relates to hard and tough tools and knives capable ofholding an edge and resisting corrosion better than conventionalmaterials used for cutting instruments, and more particularly toprocesses for making cutting instruments of Type 60 Nitinol to producetools and knives that are hard, tough, and elastic, and which arevirtually immune to corrosion.

BACKGROUND OF THE INVENTION

The development of Damascus steel in the 5th century produced a hard andtough material that was, and still is, prized for knives and swords.However, the process of manufacturing Damascus steel is arduous andexpensive, and the material is susceptible to rusting and othercorrosion, so it must be kept oiled and otherwise protected fromcorrosive influences. Because of its susceptibility to corrosion and theneed to keep it oiled to prevent such corrosion, Damascus steel is notsuitable for food preparation, skinning game or other meat cuttingapplications, so its usefulness in the real world is limited. Itsprimary application is for display knives and swords because of thedistinctive banded appearance of the material.

Since the development of Damascus steel, the most important commercialdevelopment in the field of cutlery materials in the last century hasbeen corrosion resistant steel, more commonly (although inaccurately)called “stainless steel”. Stainless steel is characterized by theinclusion of chromium and sometimes nickel in the composition whichmakes it significantly more corrosion resistant than other types ofsteels, and as a result is now very widely used in most cutlery.However, in order to obtain the hardness necessary for retaining adecent cutting edge, the material must be well above 400 on the Brinellscale, or 42 on the Rockwell C scale, and preferably above 500 Brinell.Compositions of corrosion resistant steel having high hardness have beendeveloped, such as 440C which can be heat treated to a hardness of about56 on the Rockwell C scale. That is an adequate hardness for retaining agood cutting edge, but this material also has a high carbon content ofabout 1.5% and is difficult to machine. The high carbon content resultsin reduced corrosion resistance, resulting in a tendency for the cuttingedges of knives made from this material to become dull because the thincusp of the cutting edge corrodes away, leaving a rounded edge. This isparticularly true for environments containing the chlorine ion, such assea water and chlorine cleaning solutions used in food preparationareas. The cost of knives made from 440C stainless steel is higher thanknives made from other material because processing the material andmachining the blade shape is more difficult than it is for other knifematerials. Finally, knives made of 440C stainless steel have a tendencyto lose their luster over a relatively short time because of tarnishing,stains and corrosion, resulting in a knife blade with an unattractive,dingy appearance which customers dislike.

FDA requirements for knives used in meat cutting and fish processingoperations have very stringent corrosion resistance standards whichlimit the carbon content of the stainless steel to no more than 0.10%.Corrosion resistant steels are available that meet these requirementsand knives made from them do indeed exhibit adequate corrosionresistance for safe use in meat cutting and fish processing facilities.However, these materials are soft, less than 200 on the Brinell scale,and knives made from these materials dull quickly and must be sharpenedcontinually. As a consequence, these knives last only a short timebefore they are sharpened away and are discarded. This industry has longneeded a knife that is approved for use around meat, poultry and fish bythe U.S. FDA and would remain sharp for long periods of constant usewithout sharpening.

In the field of cutting instruments other than cutlery, the mostsignificant commercially development in the last century has beensintered carbides of silicon, tungsten and titanium in a metallic matrixof cobalt or other toughening metals. Carbides are very hard and hold acutting edge better than most other materials, but they are brittle andtend to shatter when stressed beyond their yield strength. When designedproperly and used within the intended parameters of workpiece hardnessand cutter feeds and speeds, carbide cutting inserts provide long lifeto cutting tools and are very widely used throughout the industry.However, even with improvements to the matrix material, the bondinginterface between the carbides and the matrix material, and themanufacturing processes, no carbide metal matrix composite materialshave been developed that would be suitable for cutlery, and the materialremains so brittle that its use must be carefully controlled to preventshattering of the cutting instrument if the feed speed, cutter speed orthe hardness or toughness of the workpiece exceeds the stresslimitations of the carbide cutter.

Chipper and shredder blades, lawn mower blades, and brush cutter bladesare notorious for their short blade life. These blades have highvelocity and often encounter hard materials such as rocks and metaldebris in their operation, so they must be made malleable. If they weremade hard to retain a long blade life, they would be brittle and subjectto catastrophic failure in the event of impact with a rock or the likewhich could shatter the blade or initiate a crack which could growthrough the blade material and rupture at some unpredictable time in thenear future. The malleable material does not crack or shatter like theharder material would, but it is also relatively soft and the blade edgequickly becomes rounded in ordinary use. The rounded edge cuts slower,requires more energy to cut, and cuts with a ragged edge rather than aclean edge, essentially breaking rather than cutting. In large chippingoperations such as slash chipping in logging operations, theconventional chipper blades must be changed frequently, resulting inlengthy and inefficient downtime and idling of the operators. A bladematerial for machines of this nature that is hard and holds an edge, andis tough instead of brittle like conventional hard materials, would beextremely welcome to owners and operators of these machines. These sameconsiderations also apply to machines such as stump grinders and roadscarifying machines that are actually expected to involve contact withthe ground or with rocks.

Many hand tools such as axes, splitting mauls and picks have the samemalleability requirements that blades for chippers and shredders andthat sort of machine have. The cutting or leading edge must be mademalleable enough to yield or roll over on impact with a hard material sothat it does not chip or break and produce flying metal fragments thatwould be dangerous to the user or bystanders, especially to their eyes.

Tools such as pruning shears, clippers, and saws, grafting knives, andchain saws used on green plants often get gummed up with plant sap thatsticks tenaciously and is very difficult to clean off the tool. Thesticky sap interferes with smooth cutting by the tool since it preventsthe tool blade from sliding smoothly through the cut. The sap alsopromotes corrosion of the tool surfaces which makes even more difficultthe task of cleaning the old sap off the tool. The corrosion around thetool cutting edges dulls the cutting edges and also gums up thesharpening tools.

Medical cutting instruments such as chisels, files, and scalpelscurrently in use are made primarily from 300 series stainless steels,primarily because of its corrosion resistance and tendency to bendrather than chip if the instrument encounters bone. However, the 300series stainless steels are so soft that the instruments quickly becomedull and must be replaced with sharp instruments. Scalpel sharpness isvery important to a surgeon, and it is commonplace in lengthy operationsfor numerous scalpels to be used and discarded in the course of theoperation.

In the 1960's, the Naval Ordnance Laboratory in White Oak, Md. inventedan intermetallic compound of nickel and titanium which they named“Nitinol”. One form of that material, which they named “Type 60Nitinol”, has a composition of 57-63% by weight nickel and the balancetitanium The Navy was interested in this material because it wasnonmagnetic and potentially useful to the Navy Seal commandos in knivesto defuse mines or cut anchoring cables on magnetic mines during theVietnam war. The Navy had a small quantity of this material made and anexperimental program was initiated to fashion it into knives for itsSeal commandos, but the material proved to be so difficult to machinethat the contractor was unable to produce more than a few prototypes andno further knives were made, despite the desirable attributes of theknife.

Thus, there has long been a need for a cutting instrument that iscorrosion proof, hard, flexible, and tough, and can be polished to ahigh long lasting luster. This cutting instrument would have the abilityto hold an edge for a long period, even in corrosive environments suchas salt water and industrial chemicals, and it would be FDA approved foruse in meat cutting and fish processing facilities, as well as inhospital operating rooms. High production rate processes for making sucha knife at reasonable costs also have been long needed by the industryand, once adopted, will militate for the replacement of stainless steelby Type 60 Nitinol for all but the cheapest cutting instruments.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide improvedprocesses for making a cutting instrument from Type 60 Nitinol. Anotherobject of this invention is to provide an improved cutting instrumenthaving a monolithic blade with a surface finish smoother than about 20microinches and an edge hardness exceeding 55 on the Rockwell C scale.Yet another object of this invention is to provide a cutting instrumentthat is immune to corrosion from common corrosive agents, includingocean saltwater.

These and other objects are attained in a cutting instrument having ablade made from a blank cut from a plate or strip of Type 60 Nitinol.The plate or strip, having a thickness of about 0.010″-0.500″, is firstsandblasted to remove hard oxides that form during hot rolling of theplate. The blade blank is cut out of the plate using a laser cutter,abrasive waterjet or wire electron discharge machining. The blank isflattened to remove any curvature that may remain from the rollingoperation, and is surface ground to a depth of about 0.001 to 0.005inches top and bottom to remove surface imperfections in the plate. Anedge is ground into the blade blank using a PCBN or diamond grindingwheel or belt and a liberal flooding of coolant to help capture theNitinol particles. The surface of the blade can be polished to alustrous surface finish, if desired, smoother than 2 microinches RMS,using a diamond grit abrasive polishing compound.

DESCRIPTION OF THE DRAWINGS

The invention and its many attendant objects and advantages will becomemore clear upon reading the following description of the preferredembodiments in conjunction with the following drawings, wherein:

FIG. 1 is a top plan view of a knife made in accordance with thisinvention;

FIG. 2 is a side elevation of the knife shown in FIG. 1;

FIG. 3 is a bottom plan view of the knife shown in FIG. 1;

FIG. 4 is a sectional side elevation of the knife shown in FIG. 1 alonglines 4—4 in FIG. 3;

FIG. 5 is an enlarged sectional side elevation along lines 5—5 in FIG.1;

FIG. 6 is a plan view of a knife like the one shown in FIG. 1, having aknurled handle and a latching scabbard;

FIG. 7 is a plan view of the scabbard shown in FIG. 6;

FIG. 8 is a side elevation along lines 8—8 in FIG. 7;

FIG. 9 is a sectional view along lines 9—9 in FIG. 6;

FIG. 10 is a sectional view along lines 10—10 in FIG. 6;

FIG. 11 is a plan view of a second embodiment of a knife in accordancewith this invention;

FIG. 12 is an exploded plan view of the knife shown in FIG. 11, showingthe bolster, handle, butt piece and pin exploded away from the knifebody and rotated 90°;

FIG. 13 is a schematic view of a tungsten inert gas welding apparatusfor TIG welding the bolster on the knife body shown in FIG. 12;

FIG. 14 is an enlarged view, partly in section, of the knife body shownin FIG. 13, showing the bolster welded in place;

FIG. 15 is a view along lines 15—15 in FIG. 14;

FIG. 16 is a schematic view of a laser welding apparatus for welding thebolster on the knife body shown in FIG. 12;

FIG. 17 is a schematic view of an electrical resistance weldingapparatus for welding the bolster on the knife body shown in FIG. 12;

FIG. 18 is an exploded view of a heat shrinkable handle for the knifeshown in FIG. 1;

FIG. 19 is a plan view of an assembled knife made from the knife bodyand handle shown exploded in FIG. 18;

FIG. 20 is top plan view of a filet knife made in accordance with thisinvention;

FIG. 21 is a top plan view of the knife body of the filet knife shown inFIG. 20;

FIGS. 22 and 23 are side and end elevations of the knife shown in FIG.20 along lines 22—22 and 23—23, respectively;

FIG. 24 is a top plan view of a hunting knife, with an integral fingerbolster, made in accordance with this invention;

FIG. 25 is a top plan view of the knife body of the knife shown in FIG.24.

FIG. 26 is a plan view of the knife shown in FIG. 6 in a shipping andstorage box with the cover removed;

FIG. 27 is an exploded sectional elevation of the knife shown in FIG. 26and the shipping and storage box;

FIG. 28 is a plan view of a folder made in accordance with thisinvention, with the top handle slab removed for clarity of illustration;

FIG. 29 is a plan view of the folder shown in FIG. 28, with the knifeblade folded into the handle;

FIG. 30 is a schematic view of a waterjet apparatus for cutting knifeblanks from a plate of Type 60 Nitinol;

FIG. 31 is a plan view of a knife blank for the knife shown in FIG. 1;

FIG. 32 is a sectional elevation of a holding jig for holding the knifeblank shown in FIG. 31 for grinding;

FIG. 33 is a schematic view of a belt grinding apparatus for grindingthe edge of the knife blank shown in FIG. 31;

FIG. 34 is a schematic view of a belt grinder hollow grinding and edgeonto the knife blank that was edge ground in FIG. 33;

FIG. 35 is a schematic view of a belt grinder hollow grinding an edgedirectly without first grinding the edge flat as in FIG. 33;

FIG. 36 is a diagram showing the heating process for forming a hard,slippery surface material on the Type 60 Nitinol article that isintegral with the parent material;

FIG. 37 is a diagram showing the spectrum of colors that can be obtainedon the surface material of a Type 60 Nitinol article using a heatingprocess in accordance with this invention;

FIG. 38 is an exploded schematic perspective view of a razor made inaccordance with this invention;

FIG. 39 is a perspective schematic view of a razor assembled from theparts exploded in FIG. 38;

FIG. 40 is a plan view of a saw blade made in accordance with thisinvention;

FIG. 41 is a cross sectional elevation of a saw blank having teeth setin accordance with this invention and showing in dotted lines the toothmaterial that will be removed for sharpening; and

FIG. 42 is a perspective view of the saw blade shown in FIG. 40 and atool for setting the teeth of the saw blade.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings, and more particularly to FIGS. 1-3 thereof,a knife 30 is shown in the form of what could be termed a “sport knife”.The knife 30 has a knife body 32 including a blade 34 and a tang 36. Theknife body 32 is made of a single piece of Type 60 Nitinol, aninter-metallic compound of about 60% nickel and about 40% titanium byweight that was invented in the 1960's by the Naval Ordnance Laboratoryin White Oak, Md. A handle 38 is bonded to the tang 36 by an adhesivesuch as epoxy which seals the interface between the handle 38 and thetang 36; the handle is also secured to the tang 36 with rivets 40. Thehandle 38 of this embodiment is a scale or slab type handle having twoslabs 42, each secured to opposite sides of the full length tang 36.Other handle types are known in the art and can be used instead of thisfull tang scale handle 38, such as half tang scale handles, such asshown in FIG. 20, and full or partial tang one piece handles, shown inFIG. 12. The scale type handles are convenient because of the ease ofmaking the handles of exotic hardwoods, such as bloodwood, bocote, zebrawood, or canary wood. Synthetic materials may be preferred in someapplications where wood handles are undesirable or not permitted.Suitable synthetic materials for handle slabs include Zytel, areinforced nylon, Delrin (made by GE Plastics), or Lexan, apolycarbonate also made by GE Plastics. The handle materials areselected on the basis of function and appearance. For example, theexotic hardwoods are beautiful, durable and hard, but may be susceptibleto surface abrasion and other influences that could degrade theappearance of the handle, and governmental regulations restrict thetypes of handle materials that can be used in certain environments, suchas meat cutting operations. In these situations, and in situations wherethe appearance of the knife is of less importance, a synthetic materialhandle would be preferable or necessary.

A series of serrations 44 may be ground along one edge 46 of the blade34, producing sharp points 48 which are particularly effective inrapidly sawing through rope and other tough materials. The opposite edge50, as shown in FIG. 1, is hollow ground and sharpened to a sharpstraight edge, and the distal end of the blade is tapered and sharpenedalong both edges 46 and 50 to a sharp point 52. Alternatively, bothedges 46 and 50 may be hollow ground to produce two straight sharp edgestapering symmetrically to a sharp point 52.

Turning now to FIGS. 4 and 5, the attachment construction for the handleslabs 42 uses rivets 40 each having a head 54 that is flat on the topand bottom surfaces. The rivets are received in rivet holes 55 in thehandle slabs 42, and the rivet heads 54 are received in counterbores 56in the rivet holes 55, and seat against the shoulders 58 of thecounterbores 56 to hold the slabs 42 against the tang 36. A roll pin 60fits with an interference fit into an axial hole 61 drilled in shanks 62of the rivets 40. The rivet shanks 62 are received with a sliding fit ina hole 64 through the tang 36.

Type 60 Nitinol is non-magnetic and is undetectable by magnetometerscommonly used in airports and elsewhere to detect concealed weapons. Forthis reason, knives made for sale to the civilian market are made withstainless steel rivets 40 and steel roll pins 60, and may also have aniron or steel strip laid in a shallow recess on the inside surface ofthe handle slabs to make the knife detectable by magnetometers. Militaryknives would have handle slabs fastened with brass or Nitinol rivetsusing Nitinol roll pins to make them completely nonmagnetic so that theycould be used for probing for magnetic mines and the like.

Some knife users have a need for a lanyard by which the knife may besecured to their wrist or a harness or the like. Underwater divers,workers in elevated exposed places, fishermen or the like working inlocations wherein the knife would be a hazard or would be lost if itwere accidentally dropped often have a requirement for such a lanyard.For this purpose, a lanyard bushing 66 with a through bore 68 is drivenwith an interference fit into a hole 70 through the tang 36 and alignedholes 72 through the handle slabs 42. The bushing 66 is flush at its twoends with the surface of the slabs 42 and the bore 68 is chamfered atits two ends to prevent cutting the lanyard or ring 74 received in thebushing 66. The lanyard or ring 74 provides a secure attachment by whichthe knife 30 may be secured against loss as desired by the users of theknives.

The design of the handle 38 is selected for secure and comfortablegripping, even in wet or slippery conditions such as skinning anddressing game or gutting fish. As shown in FIGS. 1-3, the handle has abutt end 80 which is smoothly rounded in plan profile with a radius ofabout one half the width of the handle, preferably about 1.2 inches. Thelength of the handle is about 4.2 inches so that the smooth round butt80 comfortably engages the heel of the average size hand when the knifeis held in a natural holding manner. Forward of the butt 80, the handletapers slightly and then flares at the handle midpoint to a bulge 82which naturally fits the hollow of the palm. Forward of the bulge 82,the handle again tapers and then flares to the full width of the handleat a thumb ridge 84 adjacent the junction line of the handle 38 and theblade 34. The front edge 85 of each handle slab 42 describes a convexcurve linking the front edges of the thumb ridges on both edges of theknife 30 Several parallel grooves 86 may be cut laterally across theedge of the handle in the concave flaring surface just to the rear ofthe thumb ridge 84. The concave surface in which the grooves 86 are cutis naturally engaged by the user's thumb when cutting, and improves theuser's grip on the handle. The grooves 86 are also engaged by a latch 88on one form of scabbard to hold the knife 30 in the scabbard when theknife 30 is fully inserted in the scabbard, as described in belowconjunction with FIGS. 6-10.

The handle slabs 42 can be knurled on their plane surfaces for improvedgrip as shown in FIG. 6, especially handle slabs 42 made of Delrin orother synthetic material which tends to be more slippery than wood. Theknurling can be applied by internal ridges on an injection molding die,or for lower volume production, can be cut rapidly with a CNC engravingcutter which can also cut the rounded bevel around the edges of thehandle slabs 42.

As shown in FIGS. 6-8, a latching scabbard 90 for the knife 30 shown inFIG. 1 includes top and bottom clamshell halves 92 and 94 formed byinjection molding or the like and solvent welded or fused along awaterline junction 96 shown as a broken line in FIG. 8 since it is notactually visible after joining. The open end 98 of the scabbard 90 iscurved to match the curve of the forward end of the handle slabs 42.

As shown in FIGS. 7-10, the latch 88 includes a latch body 100 pivotallyconnected to one edge of the scabbard 90 adjacent the open end 98 by arivet 102. The latch body 100 is channel shaped along its inner edge104, as shown in FIGS. 9 and 10, having spaced legs 106 and 108 thatstraddle a portion 110 of the scabbard edge that is reduced in thicknessto provide recesses 112 that receive the legs 106 and 108. A leaf spring113 biases the latch body against the edge of the scabbard 90. The leafspring 113 is attached at its forward end to the edge of the scabbard 90by fitting into an angled slot in the edge of the scabbard 90 and thenis captured by fusing the scabbard material through small openings inthe end of the spring 113. The rear end of the latch body 100 is widenedto provide space for a thumb recess 116 by which the user may pivot thelatch 100 body about the rivet 102 against the biasing force of thespring 113 to unlatch the knife 30.

Two depending teeth 118 and 120, shown in FIG. 9 project inwardly fromthe inner edges of the channel legs 106 and 108 at the rear end of thelatch 100. The teeth 118 and 120 are shaped with a profile slopinginwardly and forwardly on their rear edges, and perpendicular to thecenterline 122 of the scabbard 90 on their forward surfaces. This shapefacilitates latching of the knife 30 in the scabbard 90 when the knifeblade 34 is inserted into the open end 98 of the scabbard 90 and thecurved front edge 85 of the handle slabs 42 and the thumb ridge 84 camsthe sloping rear surface of the teeth 118 and 120 to pivot the latchbody 100 outward about the rivet 102 against the biasing force of theleaf spring 113. When the blade 34 is inserted fully into the scabbard90 with the curved front edge 85 of the handle slabs 42 engaged with thecurved open end 98 of the scabbard, the front one of the grooves 86registers with the teeth 118 and 120, and the biasing force of the leafspring 113 rotates the latch 100 so the teeth 118 and 120 drop into thegroove 86 to hold the knife 30 in the scabbard 90. The knife 30 may bewithdrawn from the scabbard 90 by engaging the recess 116 with the thumband rotating the latch 100 to lift the teeth 118 and 120 out of thegroove 86 while sliding the knife 30 out of the scabbard. Alternativelya molded sheath may be used which is sized to fit the knife with a tightsnug fit to hold it securely in the sheath.

Turning now to FIGS. 11 and 12, a second embodiment of a knife inaccordance with this invention is shown in the style of what is usuallytermed a “survival knife” 130. It includes a knife body 132 having ablade 134 and a tang 136, to which a handle 138 is fastened by rivets140 through two spaced holes 141 in the tang 136. Preferably, the handleis injection molded in one piece with a rectangular cross-section axialpassage therethrough for sliding onto the tang 136 and securing thereonby a stainless steel butt piece 142. Alternatively, the handle could bemade in two mating slabs 144 with a central axial rectangular recessinto which the tang 136 fits snugly. The slabs can be solvent welded,ultrasonically welded, induction welded or the like to seal the slabsalong a junction line 143 where they meet on the top and bottom sides ofthe tang 136.

The rear end of the tang 136 fits into a blind mortise 145 in the buttpiece 142, and a pin 146 extends through a hole 148 in the rear end ofthe tang 136 and through a hole 150 in the butt piece 142 to hold thebutt piece in place on the tang 136. The pin 146 could be a stainlesssteel pin driven with an interference fit through the aligned holes 150and 148, or preferably is a memory metal pin, such as 55 Nitinol whichis a nickel-titanium intermetallic compound having about 55% nickel andthe balance titanium. The pin is sized slightly larger than the holes148 and 150 and is pseudoplastically elongated while in its Martensiticstate to make it longer and thinner. The stretched pin 144 is insertedinto the aligned holes 148 and 150 and heated above its transitiontemperature, whereupon the pin reverts to its original shorter thickershape which permanently locks it in place in the holes 148 and 150 withan interference fit. The handle 144 can be made slightly too long sothat the hole 148 is positioned slightly forward of the hole 150, sothat when the pin 146 is driven into the holes 148 and 150, or thememory metal pin recovers its memory shape, it will force the butt piece142 forward against the handle to create a tight fit of the handle 144between the butt piece 142 and a bolster 154 described below.

The bolster 154 is attached to the knife body 132 in a groove 156 at thejunction of the tang 136 and the blade 134. The bolster 154, shownexploded away from the knife body 132 in FIG. 12, is a rectangular platemade of 55 Nitinol having a rectangular opening 158 sized slightlysmaller than the groove 156. The tang 136 can be flared slightly fromthe butt end 160 toward the groove 156, with the width of the butt end160 sized to be received in the rectangular opening 158. The bolster 154is slid forward on the tang 136, stretching and pseudoplasticallydeforming the portion of the bolster 154 on both sides of therectangular opening 158 by about 6%. When the bolster is in the groove156, it is heated to a temperature above its transition temperature,causing it to spontaneously revert back toward its pre-deformed size.Since the groove width is slightly greater than the original size of theopening 158, the bolster 154 is slightly strained in tension in thegroove 156, causing it to be very tight in the groove 156. If it is notconvenient to grind or cut the tang with a taper toward the butt end160, the bolster can be pseudoplastically deformed on a separate fixtureand then slipped over the tang 136 for heating and restoring to itsoriginal shape.

Three other methods for attaching the bolster 154 are shown in FIGS.13-15. In all of these methods, there is no groove 156; instead, thetang 136 is straight its whole length and has a width equal to thelength of the rectangular opening 158 so the bolster slides onto thetang 136 and abuts a shoulder 162 at the junction of the tang 136 andthe blade 134. At the position against the shoulder 162, the bolster 154can be fusion welded by tungsten-inert gas welding as illustrated inFIG. 13, using a filler rod of Type 60 Nitinol to create a weldment 164between the knife body 132 and the bolster around the opening 158 asshown in FIGS. 14 and 15. The TIG welding uses a power supply 166 thatproduces high amperage, high frequency current which is conductedthrough a tungsten rod 168 to produce an electric arc that is blanketedin a protective curtain of inert gas, such as a mixture of helium andargon supplied through a separate tube 170 or, more typically, through aconcentric tube around the tungsten rod 168.

The weldment 164 is ground smooth with a radiused grinding wheel (notshown) coated with cubic boron nitride which is an effective abrasivefor grinding Type 60 Nitinol. Diamond grinding wheels will grind Type 60Nitinol also, but the diamond pattern on the grinding wheel or beltshould be random rather than ordered, to prevent the establishment offixed grooves cut by aligned rows of diamond particles on the wheel orbelt, which produces peculiar surface finishes.

Two other techniques for welding the bolster to the knife body 132 areshown schematically in FIGS. 16 and 17. A laser, such as a CO₂ laserwith a 2.5″ focal length focusing optic system 176 and a laser generator178 producing about 650 watts continuous wave, produced by CoherentEnergy Corp. in Sturbridge, Mass. produces a smooth solid weldment thatneeds little touch-up grinding in the finished knife.

In FIG. 17, an electrical resistance welding technique is illustratedschematically using a power supply 180 for producing a high amperagecurrent conducted through a cable 182 to a clip 184 attached to thebolster 154. The power supply is current controlled to maintain aconstant current despite changes to the resistivity of the Nitinolbolster as its temperature changes. In this electrical resistancewelding technique, the central opening 158 in the bolster is slightlyundersized so there is intimate contact under compression at theinterface between the bolster 154 at the inner edges of the opening 158and the tang 136 so that a fused joint is created when the material atthe interface melts under the influence of the electrical currentflowing from the bolster to the knife body and thence to a ground line186. To reduce the amount of Nitinol used in the knife, the tang 135shown in FIG. 12 may alternatively be a partial or full tang extensionof titanium welded onto the knife tang at the groove 156 or, preferably,further back on the tang 136, and embedded in the handle 144.

Instead of the handle slabs 42 or the one piece molded handle 144, adifferent type of handle may be attached to the knife tang, as shown inFIGS. 18 and 19 by shrinking a handle form 187 molded of aheat-shrinkable material onto the tang 36. The handle form 187 is sizedto slip onto the knife tang 36 of the knife body 32 shown in FIGS. 18and 19 after grinding and polishing, and to be heat shrunk onto thetang, locking into the curvilinear indentations in the edge of the tang36 when it shrinks. A variety of materials are available for this use,including semirigid and flexible polyolefins, from several suppliers,including Raychem in Menlo Park, Calif.

Turning now to FIGS. 20-23, a filet knife 200 made in accordance withthis invention is shown having a knife body 202 and a single piecehandle 204. The knife body 202 has a double wedge-cut blade 206 and ahalf length tang 208. The one piece handle has a rounded butt end 210and an opposite inner end 212 into which an axial slot is routed toreceive the tang 208.

The double wedge cut of the blade 206 is ground using the same grindingequipment disclosed above. The blade is ground to a taper from the rootof the blade adjacent the position of the inner end of the handle 204 toa sharp point at the tip 214, and is ground to a taper from the back 215to the cutting edge 216. The blade thickness at the back 215 of theblade at the root is about 0.070″ and tapers uniformly toward the tip214. This produces a slender blade that has increasing flexibilitytoward the tip 214 which facilitates meat cutting close to the bone andis an optimal size for gutting fish. The tip is very sharp and the bladenear the tip is very sharp for penetrating through the hard scales ofthe fish, and stays sharp. The slender blade is about at least 5″-7″long to reach deep into the fish. The handle is a textured or knurledsynthetic material such as Delrin, or can be Rosewood which is a closegrained, non-slip wood that stands up well to water, especially iftreated occasionally with linseed oil or food grade mineral oil. Aparticularly hard, tough and beautiful variety of rosewood is a WestAfrican Rosewood called Bubingia. The butt end of the handle has alanyard hole 218 by which fishermen in boats can secure the knifeagainst loss overboard.

The handle 204 is secured to the tang 208 with rivets 220 like therivets 40 used in the sport knife 30 shown in FIG. 1. The sameadhesive/sealant is used to seal and adhere the tang in the handle slotand to seal the rivet heads in the handle counterbores, as describedpreviously in connection with FIGS. 4 and 5.

A hunting knife 230 made in accordance with this invention is shown inFIGS. 24 and 25 having a drop-point blade 232 and a pair of slab handles234 secured to a tang 236 through holes 238 in the tang 236 withadhesive/sealant and rivets 240 like the rivets 40 shown in FIGS. 4 and5 in the sport knife 30. The hunting knife 230 has a husky 5″ blade 232about {fraction (11/32)}″ thick and one inch wide for most of itslength. It is very strong and can tolerate prying forces and impact fromdropping or throwing that would break most knives at the bolster.

The knife 230 has a knife body 244 shown in FIG. 25 as it looks as lasercut from the plate 352. An integral finger bolster 242 depends from theknife body 244 at the junction of the blade 232 and the tang 236. Thefinger bolster 242 is about {fraction (5/32)}″ wide and as thick as theknife body is, that is, about {fraction (11/32)}″. In ordinary knifematerial such as stainless steel or carbon steel, a finger bolster ofthese dimensions would be so weak or brittle that it would soon bebroken off in the normal rough handling that a hunting knife normally issubjected to. Type 60 Nitinol that is thermally conditioned as describedabove is so strong and tough that it has proven to survive impacts andother forces far in excess of what a knife would normally experience.

A storage and shipping box 250, shown in FIGS. 26 and 27 includes a boxframe 252, a top 254 and a bottom 256. The box frame 252 is made from aslab of wood such as pine or mahogany that has a central cut-out 258 inthe shape of the knife it is to hold, which is the sport knife 30 inFIG. 1. The cut-out 258 is slightly larger, but similar in shape to theoutline of the knife. The cutout may be made with a simple scroll sawor, in high volume production, may be made with a CNC router.

The top and bottom pieces 254 and 256 are wood slabs about ⅛″ thick madeof pine or mahogany. The bottom piece 256 is bonded to the bottom of thebox frame 252 with wood glue or epoxy, and the top piece 254 is screwedto the top of the box frame 252 by small wood screws 260 or is connectedby a hinge (not shown) of known design. The hinge would be used forretail sales in stores where the customer would want to inspect theknife before leaving the store, and in situations where the customerwould want to use the box to display his knife. The screws 260 could beused for catalogue sales. The box may be lined with velvet to convey asuitable aurora of quality.

A folder 305 having a blade 310 of Type 60 Nitinol is shown in FIGS. 28and 29. The folder 305 has two handle slabs 312 (only one of which isshown) riveted to each other and to a butt piece 314 by rivets 316, andriveted to each other and to a lock bar 320 by a pivot rivet 325. Thehandle slabs 312 have aligned lunette recesses 327 adjacent the rear ofthe lock bar 320 which may be pressed to pivot about the pivot rivet 325to unlock the blade. The lock bar 320 has a lug 330 on its front end,remote from the butt end, which engages a notch 335 on a rounded surface336 at the root end of the blade 310. Engagement of the lug 330 in thenotch 335 prevents the knife blade 310 from inadvertently folding ontothe fingers of the user during use. The blade may be unlocked bypressing on the butt end of the lock bar 320 which pivots about thepivot rivet 325 to lift the lug 330 out of the notch 335 releasing theblade 310 to fold about a pivot pin 338 to its closed position shown inFIG. 29. A superelastic Nitinol spring 340 fitted into a slot 342 in thebutt piece 314 biases the lock bar 320 to its locked position. A shortscrew 344 with a protruding solid screw head is threaded into a threadedhole along the spine of the blade to facilitate one-handed opening ofthe blade 310. The screw 344 may be removed and threaded into the holefrom the other side of the blade for left-handed users. The hole in theType 60 Nitinol blade may be threaded using the process described in myprior U.S. patent application Ser. No. 08/349,872 entitled “ThreadedLoad Transferring Attachment”.

The handle slabs 312 are made of titanium alloy such as the widelyavailable 6-4 alloy, and each has a through hole drilled at its frontend slightly smaller than the diameter of the pivot pin 338. A slightlylarger hole 346 is drilled through the root end of the blade 310 forreceiving the pivot pin 338 with a snug sliding fit. The pivot pin 338is made of Type 60 Nitinol and is extremely strong, wear resistant andelectro-chemically compatible with the blade 310 of the same material.The pivot pin 338 is pressed with an interference fit through the holesin the two handle slabs 312 and slides in the hole 346 in the bladeroot, securing the handle slabs to the blade and laterally supportingthe blade root between the two titanium slabs 312. The tight sliding fitbetween the inside surfaces of the titanium handle slabs and the bladeroot provides long life bearing support for the blade against lateralloads, and the high strength and wear resistance of the pivot pin 338ensures a long life free of looseness that conventional folders areoften cursed with.

Processes

The processes of making the knives in accordance with this inventionwill now be described. The processes will be described with relation tothe sport knife 30, but the same processes are applicable to any otherknife design within the scope of this invention.

The knife body 32 is made from a knife blank 350 cut from a plate 352 orsheet of Type 60 Nitinol hot rolled to about {fraction (3/16)} inch.Type 60 Nitinol is a very hard material even before heat treating, andis difficult to cut, drill and grind. Its hardness and corrosionresistance make it an ideal material for cutting instruments which, whenmade of materials such as carbon steel or 440C “stainless” steelconventionally used for cutting instruments, often rust or corrode firstat the thin cutting edge and lose their sharpness in this way. However,the properties that make Type 60 Nitinol ideal for cutting instrumentssuch as knives, also make it very difficult to cut, drill and grind.

Ingots of Type 60 Nitinol are made by mixing the powered nickel andtitanium sponge and melting the composition in a crucible whilethoroughly homogenizing the chemical composition by thermal treatment.The ingot is formed into a slab about 2″ thick by hot forging. Theforged slab is heated to about 850° C. to 900° C. and rolled in arolling mill. Repeated passes through the rolling mill are necessary,with reheating of the slab when it cools below about 700-800° C. Type 60Nitinol is described in Military Specification MIL-N-81191A and isavailable from Metaltex International Corp. in Albany, Oreg.

During rolling, the sheets or plate 352 develop an oxide surface layerthat makes subsequent grinding operations slower and less efficient.This surface oxide layer may be removed by sandblasting the knifeblanks, but it is preferable to sandblast the entire plate 352 with agarnet or other medium before cutting the blanks 350 out of the plate.Garnet is faster and does a more through job than sandblasting withsand.

Attempts to machine Type 60 Nitinol have usually proven unsuccessful,but I have discovered that it can be quickly cut using abrasivewaterjet, illustrated schematically in FIG. 30. The sheet 352 isoriented with the direction of rolling parallel with the long axis 354of the blank 350 to give the greatest strength along the long axis.Water from a reservoir 356 is pressurized to about 55,000 psi in a pumpsystem 358 and directed through a nozzle 360 in a jet about 0.005-0.010thick, entraining garnet abrasive particles injected from an abrasiveinjector 362, will cut Type 60 Nitinol {fraction (3/16)} inch thickplate at about 18 inches/minute. The waterjet apparatus is availablefrom Flow Industries in Kent, Wash. Preferably, the cutting is doneunder water to ensure capture of the Nitinol dust and to suppresssparking and fumes generated during cutting operations on Nitinol. Thewaterjet will cut several stacked plates, preferably with a rollingpressure foot that maintains the plates in contact at the cutting point.However, I prefer to cut the plates in a single thickness since thewaterjet tends to diverge and produce a wider kerf as the distance fromthe nozzle increases. The nozzle movement apparatus is digitallycontrolled by an CNC controller, so the knife blanks 350, shown in FIGS.30 and 31, can be cut automatically out of the Nitinol plate 352 oncethe pattern is programmed into the controller. The cutting operation islabor efficient and can be performed at night, so most of the costs ofproducing the blanks 350 are in the Nitinol material costs and cuttingmachine time. Although substantially more costly than 440C stainlesssteel, the superior functional characteristics of corrosion resistance,increased hardness and toughness, and 23% lighter weight provided byType 60 Nitinol blades more than justify the increased cost.

The rivet holes 64 and the lanyard bushing hole 70 are also cut with theabrasive water jet. The hole 70 is an interference hole, so it is reamedafter abrasive waterjet cutting with an abrasive reamer having cubicboron nitride particles adhered to its surface.

Another method for cutting the knife blanks 350 out of the plate 352 ofNitinol is wire electron discharge machining (EDM). Although this methodis slower than waterjet cutting, it produces a smoother edge thatreduces or may entirely eliminate the need for finish edge grinding ofthe tang 36. Wire EDM machines are available from several sources,including Mitsubishi EDM, MC Machinery Systems, Inc. and Hansvedt, Inc.commercially available from Perine Machine Tool Corporation in Portland,Oreg. in various forms.

A third and preferred technique for cutting the knife blanks 350 fromthe plate 352 is laser cutting. Laser cutting has proven to be an idealtechnique for cutting blanks 350 out of the plate 352 because the laserkerf is very narrow and wastes only a tiny amount of material. Thesurface finish of the cut edges of the blank 350 is remarkably smoothand requires little or no finish grinding around the edge of the tang 36before polishing the finished knife. The precision of the guidanceapparatus which guides the material under the laser cutting head is soaccurate that the holes 64 and 70 in the tang 36 can actually be used ascoordination features to fixture the knife blank for edge grinding.

The laser apparatus used to cut the blanks 350 out of the plate 352delivers a power of 2600 watts at the cutting point. A high pressureinert gas jet is directed at the cutting point to blow molten materialout of the kerf. The laser apparatus is made by Trumph ManufacturingCompany. When cutting Type 60 Nitinol plate about {fraction (3/16)}thick, a cutting speed of about 100 inches/minute or more can bemaintained.

The high speed and excellent surface quality of the laser cutting isunexpected in view of the difficulty encountered using conventionalprocesses to cut Type 60 Nitinol. I believe that the laser cutting worksso well because of a combination of four factors: low thermalconductivity, low specific heat, low coefficient of thermal expansion,and the single phase nature of Type 60 Nitinol. The low thermalconductivity ensures that heat remains concentrated in the cutting zoneinstead of being conducted rapidly away as in more conductive materials,and the low specific heat ensure a rapid temperature increase at thecutting point, resulting in rapid melting of the material under thelaser beam. The single phase material does not change its propertiessignificantly as its temperature increases so it is very stable. Thedimensions of the material are affected very little by the heat input bythe laser because of the above factors and because of its lowcoefficient of thermal expansion, further enhancing its stability duringlaser cutting. Laser cutting of Type 60 Nitinol that uniquely combinesall these factors is fast and produces smooth cuts of unparalleledspeed, accuracy and precision.

The plate 352 as delivered from the rolling mill sometimes has aresidual curve in the direction of the last rolling pass, usually thelong direction. This curve must be removed from the blank 350 beforesurface grinding and edge grinding since otherwise the finished knifewould have an objectionable curve out of its flat plane. It is possibleto grind the blanks 350 flat, but it is difficult to mount a curvedworkpiece on a flat bed of a surface grinder, and grinding a curvedblank 350 to make it flat is time consuming, costly and wastes material.A preferred technique for straightening a curved knife blank 350 is toheat it to about 800° C.-900° C. and then press the hot blank 350against a flat surface, holding it there until it cools to roomtemperature. After cooling, the blank remains straight, with little orno springback. One simple method is to clamp the hot knife blank betweenthe jaws of a vise. Care must be taken in handling hot knife blanks 350of Type 60 Nitinol since the very low thermal conductivity of thematerial results in a long cool-down time for a hot knife blank. Theknife blank 350 is about {fraction (3/16)} thick before surfacegrinding, so it cools much more slowly than a thinner blade, such as thefilet knife blade shown in FIGS. 20-23.

The plate 352 as received from the rolling mill may be somewhat brittlebecause the rolling process may involve rapid quenching of the hotNitinol by cool rollers. Rapid quenching of the Type 60 Nitinol cangreatly increase the hardness of the material and reduce itsmalleability so that it becomes brittle as well as hard. A heatconditioning step reduces the hardness of the blank 350 to a more easilyground hardness of about 50-55 RC and increases the toughness of theblank 350 so that it is unbreakable by any kind of influence that aknife would normally be expected to encounter. The heat treating step isto heat the plate 352 or the knife blank 350 to a temperature of 600°C.-900° C. and allow it to cool slowly in air to room temperature. Thissimple process eliminates the internal stresses in the internal twinningboundaries that is believed to produce the greater hardness when thematerial is heated and then quenched quickly.

Since Type 60 Nitinol is non-magnetic and cannot be magneticallyattached to the bed of a surface grinder, an adapter 366, shown in FIG.32, may be used to grip the blank 350. The adapter has a pair of stubpins 368 and 370 that can be moved toward or away from each other by ascrew 372 having right handed threads on one end and left handed threadson the other end. The stub pins fit into the holes 64 in the knife blank350 and are moved in opposite directions by rotation of the screw 372 tohold the knife blank 350 securely on the flat upper surface 374 ofadapter 366. The adapter 366 has a flat steel base plate 378 that issecurely attached to the bed of a surface grinder by an electromagneticholder on the grinder bed.

Surface grinding of the knife blank 350 removes surface blemishes andmicrocracks that may be created when the plate 352 is hot rolled, andreduces the thickness of the blade 34 to the desired thickness for thatparticular style knife. Boning knives and filet knives like the knifeshown in FIGS. 20-23, for example, have thinner blades than generalpurpose hunting knives like the knife shown in FIG. 24, or the blade ofthe sport knife 30 shown in FIG. 1. Surface grinding can be performed byconventional grinding equipment, but the best abrasive I have found forgrinding Type 60 Nitinol is diamond or polycrystalline cubic boronnitride (PCBN). The PCBN is preferred because it is much less expensivethan the diamond and tends to be distributed in a random pattern on thegrinding surface, whereas diamond is often distributed in an orderedpattern that produces peculiar patterns on the finished surface. Agrinder that enables easy and convenient changing of the grindingsurface for successive stages of increasingly finer mesh grit is thebelt grinder. PCBN and diamond grinding belts are available from the 3MCompany in Minneapolis, Minn.

Grinding of Type 60 Nitinol is fundamentally different from grindingconventional materials. Steel may be ground in a relatively softcondition before heat treating to the desired hardness, but Type 60Nitinol is always hard. Moreover, it is best to avoid overheating theType 60 Nitinol at the grinding face because at high temperatures, thematerial galls and the temperature increases rapidly, distorting theblank and shortening the life of the belt. More seriously, high surfacetemperatures produced by slow feed rates and deep cutting passes inconjunction with the use of cutting or cooling fluids can productmicrocracks in the ground edge of the knife. The low thermalconductivity of the Type 60 Nitinol makes it very difficult to removethe heat once the blank has gotten hot. The surface may be flooded withcoolant to removing heat and lubricate the grinding face duringgrinding, but if coolant is used it is best to ensure that the surfacetemperature is not elevated above about 500° C. to prevent rapidquenching and resultant brittleness, which can result in microcracks atthe cutting edge of the knife. The coolant bath also helps to trap theparticles of Nitinol removed by grinding. To reduce the rate of heatingand work input into the material during grinding, the surface grindingis performed by rotating a grinder having abrasive particles on acutting surface of the grinder against the Nitinol workpiece at asurface speed of about 5000 to 7000 surface feet per minute and grindingwith a very shallow depth of cut, about 0.001-0.005 inch, preferably0.001-0.002 inch, and as high a feed rate as the material will tolerate.This cutting schedule prevents heat build-up and enables removal of heatin a spray of coolant and helps to trap the grinding dust removed fromthe parent material. The feed speed is slower than the grinding feedspeed with conventional materials, on the order of about 50-120inches/minute despite the shallow depth of cut because the material cutsso slowly, but should be as fast as possible to minimize the heatbuild-up in the knife edge. The coolant spray entrains the grindingdust, facilitating capture of the dust in the recirculating coolant andminimizing the health risk presented by Nitinol dust.

After surface grinding, the edges are ground to a taper of about 5°-10°as illustrated in FIG. 33. These surfaces are ground by tilting thegrinder or tilting one end of the knife blank 350 up about itslongitudinal axis on a modified adapter 366′ and passing the knife blank350 lengthwise with the axis of the blank perpendicular to therotational axis 380 of the grinding wheel or drum 382 of a belt grinder384 so the belt 386 engages the surface on a tangent. This produces aflat edge surface 388 which can be sharpened directly. The blank canalso be hollow ground, as illustrated in FIG. 34, by turning the blank900 and tilting the axis of the blade slightly away from the axis 380 ofthe drum 382 so they are not exactly parallel. The blade is moved alongthe surface of the drum 382 while the belt or grinding wheel grinds thehollow or concave surface to produce a hollow ground edge 390.

The edge can be ground from the blank directly as shown in FIG. 35. Theblade blank 350 is mounted on a modified adapter 366′ (shown in FIG. 33)at the desired blade angle, and the axis 380 of the drum 382 or grindingwheel is tilted slightly away from the direction of elongation of theblade blank 350. The blade blank or the grinder 384 is moved parallel tothe direction of elongation in a series of rapid shallow passes thatremove 0.001-0.002 inch of material at each pass. The blank is flippedand rotated for grinding the other blade edge surfaces. A blade can becompletely edge ground in about ten minutes in this way. The final passcan be with a belt 386 having a finer mesh grit size to produce a finersurface so that less work is needed during the polishing step.

Edge grinding and surface grinding can momentarily raise the surfacetemperature of the knife edge to a high temperature which is thenquenched by the coolant spray, producing a heat treatment that raises atleast a shallow surface layer to a high degree of hardness. The hardnessis especially undesirable at the edge of the blade because, although itis very hard, it can chip if hit hard against an edge of a hard itemsuch as a rock. Indeed, the Type 60 material in its as-rolled conditionis so brittle that a knife blank can actually be broken by hand and canbreak if dropped on a concrete floor from about four feet In thepolishing operation, the knife body can be exposed to severe conditionsof bending and is occasionally dropped or thrown by the buffing wheels.To prevent chipping or breakage caused by hitting or dropping the knifebody while in this state of undesirable hardness/brittleness, it isdesirable to heat treat the entire knife blade after grinding by heatingit to about 400° C.-600° C. and allowing it to cool slowly in air toroom temperature. An easy and reliable indication of reaching the properheat treating temperature for this purpose is a change of color of theType 60 Nitinol surface from silver to gold. The surface coloringprocess is discussed in detail below.

Blades with a long tapering tip are easily overheated with a torch andthe thin material at the tip can cool very quickly in air, producingexcessive brittleness in the tip. To prevent such knives from reachingthe customer, I drop the knife tip first onto a concrete floor fromabout 4 feet. If the tip breaks, I merely regrind the tip of the bladeto shape, taking care not to raise the temperature above about 500° C.to avoid the same problem from recurring.

The blade is now polished to a finish of about 20-10 micro-inches orfiner, down as fine as 5-1 microinches. If the preceding grindingoperation produced a blade finish that is too rough, it may be ground toa finer surface finish using a belt with a fine aluminum oxide abrasive,although it is preferable that the final pass in the grinding operationbe performed with a fine grit grinding surface to minimize the polishingeffort. A rough polishing operation follows, using Turkish emery gluedto a buffing wheel with a suitable adhesive, such as horseshoe cement. Ahigh power motor, on the order of 10 hp, removes surface material,including the gold surface material, producing a luminous plume ofsparks. It is necessary to protect workers in the vicinity of thepolishing operation from the sparks and the dust with capable exhaustand dust collection equipment. The final polishing is performed with abuffing wheel impregnated with a fine diamond polishing compound. Abuffing compound that I have found to be particularly effective is GlazWoch, available from Ralph Maltby in Newark, Ohio. Contrary to the usagesuggestions of the distributor, the Glaz Woch is very effective forproducing a mirror-like sheen on the polished Type 60 Nitinol bladeusing a buffing wheel driven at about 3000 RPM with a 10 HP motor andhigh buffing pressure. Other polishing compounds are available from 3Mcorporation in multiple mesh grades which, like the series of ever finergrit mesh on the grinding belts, may be applied in descending mesh sizeusing a different buffing wheel for each different grit size. Otherbuffing compounds that also produce a fine finish are E5 Emery followedby SCR Stainless, produced by Dico Brothers Company in Utica, N.Y. Thefinish resulting from these polishing operations has an extremelyattractive mirror-smooth appearance that is not degraded over time bystains, corrosion or tarnishing like the finish on conventionalmaterials.

Ornamentation, logos, trademarks and other indicia can be permanentlyengraved into the blade 34 by an electrochemical process that flowsdirect current through a transfer medium on which the desired indicia isreproduced. The transfer medium, which allows the current flow onlywhere the etching action is desired, is placed directly against thesurface of the blade where the indicia is to be engraved and an acidsoaked pad is laid over the transfer medium. A conductor connects thepad to a transformer, and a ground conductor grounds the blade back tothe transformer. The blade surface and the transfer medium must be veryclean and the ground conductor must be placed as close as possible tothe engraving location since the electrical conductivity of Nitinol islow. The transformer is turned on to produce a DC current of about 5amps, and the process is allowed to run for about 20 seconds. Thecurrent is then turned off and the pad and transfer medium are removed.The knife blade and transfer medium are rinsed in water to remove tracesof acid and the engraving of that blade is complete. The etching is donebefore the surface treatment to be described immediately below becausethe surface material is non-conductive.

The blade 34 can be processed to have a hard, non-stick, light or darkgray, chemically inert and electrically non-conductive surface. Theprocess begins after the knife blade has been polished to as smooth asurface as is economically feasible. The smoother the finish is to startwith, the better the finish will be after the surface conditioningprocess is done. As shown in FIG. 36 the process begins with heating theblade to an elevated temperature, believed to be about 600° C.-900° C.in air for about 2 minutes. I have found that it is necessary to heatthe blade outdoors in cold air, at an ambient temperature of about 0-32°F. I have not determined why these conditions are necessary to producethe gray color, but I believe it may be related to the cooling rate orthe difference in air constituents outdoors vs. indoors. Minordifferences in CO₂, O₂, N₂ and water vapor concentrations indoors vs.outdoors may influence the reaction. I believe that the gray color ofthe surface material is a chemical reaction that produces oxides,nitrides, carbides or other compounds from the nickel-titaniumintermetallic compound of the Type 60 Nitinol. Whatever the reaction is,if indeed it is a reaction, I produce it by heating the knife bladeevenly with a MAPP gas torch until the gray color forms, and then removethe torch and allow the blade to cool naturally in air. The coolingoccurs slowly because of the low thermal conductivity of Type 60Nitinol, so I allow 30 minutes or more cooling time before the nextstep.

When cool, the blade is polished with a fine grit diamond buffingcompound such as Glaz Woch mentioned previously, but is not subjected tothe high power and high pressure buffing that produced the high glossfollowing the surface and edge grinding. A lighter pressure and lowerpower wheel, on the order of one HP, is necessary, otherwise the surfacematerial could be polished off. After buffing, the blade will be amedium gray color and will have a smooth, shiny surface finish. The heattreatment is repeated to the same temperature and for about the sametime period and conditions, and after cooling, is again polished withthe same buffing steps. The process may be repeated several times toproduce darker shades of gray and increasing luster of the surface.

The resulting surface is a lustrous dark gray and is so hard andslippery that it is virtually scratchproof and non-stick. It ischemically inert so it can be used in environments that would beextremely destructive to conventional knife materials. The surface iselectrically nonconductive so its use around electrical equipment wouldprovide an extra margin of safety to workers. For applications such aspruning shears, clippers, and saws, grafting knives, and chain saws thatare used on green plants, the plant sap is easy to clean off the tooland the blade is so slippery that it slides smoothly through the plantbeing cut. The corrosion resistance ensures that the blade remainssmooth and slippery and the edge remains unaffected by the sap thatcauses corrosion in prior art blade materials.

For military application in which a shiny knife blade is undesirablebecause of the glint that reflection from the sun or sky produces, anon-reflective matte finish can be produced by glass-blasting the bladesurface before the surface conditioning process. Glass-blasting usesmicron sized glass beads driven against the blade surface at highvelocity to produce a smooth but matte or non-shiny finish. The finishis similar to that produced by sand-blasting with garnet, except thatthe surface irregularities on the glass-blasted surface are smaller thanthe garnet-blasted surface.

A modification of the above surface conditioning process can be used toproduce a similar surface, but with any of a spectrum of colors ratherthan gray. As shown in FIG. 37, the colors, gold, red/purple, blue,silver, and green may be obtained in the Type 60 Nitinol surfacematerial, depending on the degree to which the Nitinol is heated. Theprocess is similar to that used to achieve the gray surface material,but the process is performed indoors at room temperature, between 60° F.and 80° F. This process also starts with polishing the blade to assmooth and shiny a surface finish as is practicable, since a shinyfinish is even more important to the appearance of a colored blade thanit is to a black or gray blade. In fact, I have not found it to bepossible to produce any colors other than gray on a glass-blasted bladesurface; some degree of polishing is necessary to get the colors shownin FIG. 37. After polishing, the blade is meticulously cleaned to removeall traces of oil or other residue that could bum onto the blade at hightemperature and leave marks in the colored surface. The blade is heatedto a temperature at which the desired color appears on the surface ofthe blade. The colors begin to appear at a temperature in the range ofabout 400 C°-650° C. As shown in FIG. 37, the colors appear and changeas the temperature increases. Light gold is the first color to appearand, in order, the color changes to darker gold, red/purple, dark bluelight blue, and then silver, but a lighter shade of sliver than theoriginal shade of the polished Type 60 Nitinol material. If thetemperature is raised even higher after the light silver color appears,the blade color again passes through the gold, red/purple and bluecolors as before, but then goes to green. The temperature changerequired to pass through the second color spectrum after the lightsilver is a narrow temperature band and can happen so fast that it mightnot be noticed. It appears that third and fourth color spectrums withthe same colors follow the second spectrum, and there may be more afterthe fourth, but the temperature difference becomes smaller between thespectrums so they are difficult to discern. After heating, the blade isallowed to air cool and may be buffed with a fine diamond grit such asthe Glaz Woch material mentioned above. All of the surface materialshave the same hard, slippery (non-stick), electrically nonconductivecharacteristics of the gray surface material discussed above.

Curiously, the indicia etched into the surface of the blade as describedabove does not take on the color that the blade surface assumes. Ibelieve this may be the result of a rough surface formed by theelectrochemical action of the etching process, but whatever the reason,the result is a remarkable enhancement of the readability of the indiciaon the colored surface.

If the desired color is, say, dark blue and the blade is mistakenlyheated to a temperature at which a subsequent color appears, it ispossible to proceed through silver to the second spectrum to recreatethe desired color. Doing so is more difficult because of the narrowertemperature band within which color changes occur. In practice, it maybe preferable to accept the silver color or polish off the surfacematerial with a high power buffing wheel impregnated with diamondbuffing compound and repeat the heating process.

The colored blade surface materials I have produced are with the use ofa hand-held torch, applied judiciously to obtain the desired color.However, I anticipate that mass production of knives to produce thesedesirable surface materials would be done in an electric furnace whereintemperature and atmospheric conditions could be precisely controlled.The knife tang could be mounted in a holding fixture which would bemoved through a pass-through furnace in which the necessary atmospherewould be maintained and the temperature would be raised to thatnecessary to produce the desired surface material. The fixture wouldthen be moved out the other end of the furnace and the knives would beair cooled in preparation for the final assembly steps to complete theknife. Alternatively, the heat processing could be a batch operationwhich would be slower but would have better control of the cooling rate.

The above coloring process could be used to make other Type 60 Nitinolarticles such as jewelry. Type 60 Nitinol is body compatible and couldbe used to make gold colored ear rings and finger rings in which jewelscould be securely mounted. Gold mountings for jewels in rings are soweak that it is commonplace to lose the jewels by catching the mountingprongs on clothing and the like, bending the prongs so the jewel fallsout. A Type 60 Nitinol ring heat treated to a gold color would havemounting prongs so strong that loss of jewels would become a rareoccurrence.

After polishing and heat treating to obtain the desired color tone onthe blade and the edge of the tang 36, the handle slabs 42 are alignedwith the tang 36 and the rivet holes 55 and bushing hole 72 are backdrilled in the slabs 42, using the rivet holes 64 and the bushing hole70 in the tang 36 as drill guides if the holes are not already drilledduring the cutting of the slabs 42. The counter-bores 56 are drilled inthe handle slabs 42 using a pilot counterbore drill guided by the holes55, and the rivets 40 are inserted in the holes 64 in the tang 36. Anadhesive/sealant is applied to the inside surfaces and the counterbores56 of both handle slabs 42, and to the axial holes 61 in the rivetshanks 62. A roll pin 60 is inserted into the axial holes 61 in therivets on one side of the handle and the rivets are inserted into therivet holes in the handle slabs 42. The handle slabs 42 are aligned andapplied on the tang 36 and the rivets 40 are pressed together to seatthe roll pin 60 in the axial holes 61 in the rivet shanks 62 and theengage the underside of the rivet heads 54 with the shoulder 58 of thecounterbore 56. A preferred adhesive/sealant is a modified epoxycomposition called Permabond Grade 309 made by Permabond, Int'l., adivision of National Starch and Chemical Co. in Englewood, N.J. Thiscomposition adheres the handle slabs 42 to the tang 36 and adheres theroll pin 60 in the axial holes 61 to provide enhanced retention inaddition to that provided by the roll pin 60 by itself. Theadhesive/sealant also seals the interface between the handle slabs 42and the tang 36, and seals the rivet head 54 in the counterbore 56.After curing, it is inert to the environments encountered where knivesare used, and is a food-grade material, approved by the FDA for use inmeat cutting operations.

After the adhesive/sealant is cured, attached handle slabs 42 made ofwood may be saturated with linseed oil or food grade mineral oil to sealthe wood pores against water, and the slabs are polished with a buffingcompound, preferably the Glaz Woch, available from Ralph Maltby inNewark, Ohio. The polished handle is very smooth and the attractivegrain of the exotic hardwood shows clearly and is set off beautifully bythe mirror sheen of the polished blade. Even though the handle is verysmooth, it is not slippery and can be securely gripped by hand, evenwhen wet.

The last step in the process for making the knife is sharpening theedge. The hardness of the Nitinol material makes it possible to obtainan extremely sharp and potentially dangerous edge on the blade whichcould be injurious to workers manufacturing the knife, so edgesharpening is postponed to the last step. To avoid prematurely producinga sharp edge on a hollow ground blade that could potentially bedangerous if the ground blank is not handled carefully, I leave anunsharpened edge of about 0.030 thickness which an be quickly sharpenedas the last step. The final sharpening step produces an edge of about7.5° from the centerline, or 15° edge-to-edge. This edge is ground ontothe cusp of the hollow ground surface 390 or the wedge cut surfaces toproduce a durable, razor-sharp edge on the knife. The sharp cusp of theedge is virtually immune to corrosion or tarnishing which normally dullsan edge in knives and other cutting instruments made of conventionalmaterials. Strong chlorine cleaning solutions eat away the edge ofconventional stainless steel blades resulting in dulling of the edge asquickly as overnight, even if the knife is not used. Such strongchlorine cleaning solutions have no significant affect on the Type 60Nitinol knife so the blade edge remains as sharp despite exposure tothese solutions. Moreover, the blade is so hard and tough that itretains its sharpness, even when cutting hard materials such as hemp andfiberglass, for much longer than conventional materials, especiallystainless steels that are formulated to resist corrosion by lowpercentages of carbon.

The processes described above can also be used for making cuttinginstruments other than knives. For example, a razor blade 400 in adisposable cartridge 402 permanently or removably mounted on a handle404 as shown schematically in FIGS. 38 and 39, can be made from a rollof thin gauge Type 60 Nitinol strip material mounted in a plastic base406 that is held by or integral with a handle. Such blades are extremelysharp and stay sharp for an extended period of use, despite theirexposure to soap, water, and high humidity. Their higher cost is offsetby the extremely long life and extreme sharpness during the long life.The primary cause of dulling of razor blades is corrosion of the bladematerial at the cusp of the blade edge and, to a lesser extent, erosionof the corroded edge material by the beard stubble. Even when the razorblade does not appear corroded, there is a small degree of corrosionconcentrated at the cusp of the edge which rounds off the cusp and dullsthe edge. Type 60 Nitinol resists this corrosion far better thanstainless steel and also has the hardness and toughness to resisterosion of the cusp from which softer stainless steel formulationssuffer.

The blade 400 has attachment structure by which it is mounted in thebase 406. The attachment structure shown in this embodiment includes apair of holes 408 which receive plastic pegs 410 that are heat softenedand deformed to hold the blade 400 down against the base 406 as shown inFIG. 39. If the blade 400 is to be mounted to self align to the profileof the skin to be shaved, it can be a much thinner and narrow strip ofType 60 Nitinol sharpened along one edge and spot welded by resistanceor laser welding to a titanium support bracket that is spring loaded ina slot in the cartridge that clips into the handle in conventionalrazors.

The narrow strip of Type 60 Nitinol is slit from a sheet of type 60Nitinol hot rolled to a thickness of about 0.015-0.050 inch. Theslitting is preferably done by gang roller shears or gang laser cuttersand the strips are manipulated by a vacuum handling system. For razormanufacturers that prefer to use the same cartridge fabrication machinesthey currently use, the individual strips are laser welded end-to-endand rolled in a large coil that can be used in the continuous high speedautomated sharpening and cartridge fabrication machines now used to makerazor cartridges. The strip of Type 60 Nitinol may be heat treated to ahardness of about 62 on the Rockwell C scale by heating to about 600° C.and rapidly quenched. The edge, hardened in this manner, is fairlybrittle, but it is protected in the mounting handle or cartridge againstimpacts so the hardness is not a detriment in this application. The onlydetriment, if it could be call that, is the extremely long life that arazor blade of Type 60 Nitinol has. Its immunity to corrosion in thepresence of environmental influences that commonly degrade the sharpnessof conventional blades, and its erosion resistance to beard stubble,makes the Type 60 Nitinol razor last so long that widespread adoption ofthis technology by the razor industry will greatly reduce the totalsales volume of razor blades.

Medical instruments such as scalpels, chisels and files made of bodycompatible and FDA approved Type 60 Nitinol would be very safe for usein the operating room because of the body compatibility, and would staysharp for long periods of use. Scalpel blades are now normally discardedafter use, but Type 60 Nitinol blades would be so long lasting andcorrosion resistant that they could be sterilized and reused many times,resulting in much less waste of medically dangerous waste and greatlyincreased efficiency of hospital operating rooms. Type 60 Nitinol takesan extremely smooth finish and is very slippery, so its use as scalpelblades would be ideal because it would cut through skin and toughcollagen with no tendency to stick in the incision.

Cutter inserts for the blades of stump grinders, brush cutters, lawnmowers, chipper/shredders, etc. would be sharp and stay sharp becausethe Nitinol is hard and tough, not brittle, so there is little danger ofthe blade material shattering and producing dangerous shrapnel.

Food processor, blender, and coffee grinder blades likewise would bemade with much harder and tougher cutting edges that would stay sharpand never rust or corrode. The high impact that blender, food processorand coffee grinder blades experience require that they be made of steelformulations that are not brittle, but the non-brittle steels are softand do not hold an edge. Type 60 Nitinol is hard but tough; it will notshatter or chip on impact if it is thermally conditioned as describedabove.

Conventional camp saws are made of high carbon steel so that the sawteeth can be tempered to a high degree of hardness, but the high carbonsteel rusts quickly if it is exposed to moisture and not immediatelydried and oiled. That much care is difficult to provide in the field, socamp saws often become rusty and dull. A Type 60 Nitinol saw blade 415,shown in FIGS. 40 and 41, will not rust and yet it is naturally hard, onthe order of 53 on the Rockwell C scale, and has a cutting edge 430 thatcan be heat treated to a hardness of 62 or higher on the Rockwell “C”scale.

The saw blade 415 is cut out of a sheet of Type 60 Nitinol hot-rolledfrom a hot forged ingot of Type 60 Nitinol by laser cutting at a highcutting rate, on the order of 100 inches/minute or higher. This producesa flat, elongated blade blank having two planar faces and a direction ofelongation 417. Attachment structure at one or both ends of theelongated saw blade, in the form of notches or holes 420 as shown inFIG. 40, and pointed cutting teeth 422 are cut into the profile of thesaw blank at the same time that the saw blank is cut out of the sheet.

As shown in FIG. 42, the teeth of a Type 60 Nitinol saw blade 415 can beset by heating the toothed edge of the saw blade to a high plastictemperature, preferably red hot, to reduce its yield strength andelasticity. At a temperature of above 500° C., preferably about 650° C.,the Type 60 Nitinol can be plastically deformed and, if held in thedeformed position while it cools to below about 400° C., will retain itsdeformed position with no springback. The saw teeth 422 are set byheating to the high plastic temperature and forcing a tool steel die425, having alternating beveled ramps 427 and recesses 429 machinedtherein at the saw teeth locations, to bend the teeth 422 laterally outfrom the plane of the blade in alternating directions. The die 425 isheld closed while the teeth 422 cool in their set positions, and is thenopened for removal of the saw blade blank 415.

The teeth are ground sharp along one or both inside edges, as indicatedin FIG. 41, by a narrow grinding wheel or disc, preferably havingdiamond or PCBN abrasive particles embedded in its surface. For highvolume production, the grinding discs are ganged on an apparatus thatgrinds the edges on one side of all the teeth on one side of the bladeat the same time. The grinding discs do not last as long as they lastwhen grinding conventional steel saw blade material which is hardenedafter grinding, but the amount of Type 60 Nitinol that must be removedto sharpen the saw teeth is small, so the discs can be made to last longenough to be economical, especially considering the greater price that acorrosion-proof saw can command in the market place.

After grinding, the saw blade is heat conditioned as noted above toremove any brittleness in the teeth resulting from excessive heatingduring grinding. The saw blades are cleaned and assembled on a holdingfixture and inserted into an oven where they are raised to thetemperature at which the gold color appears on the surface, about 500°C. They are then allowed to cool slowly in the oven to a temperaturebelow about 400° C. and are removed from the oven. The entire blade isnow tough, springy and strong, and is at about 50-53 on the Rockwell Chardness scale. To increase the hardness of the teeth without creatingexcessive brittleness, the toothed edge 430 is heated by inductionheating which raises the temperature of the teeth to a desired hightemperature in the region of 500-600° C. The heating is done in acontrolled temperature environment in which the cooling rate can becontrolled to prevent excessively rapid cooling of the teeth that wouldcause brittleness. The temperature to which the edge portion of theblade is raised can be set to produce a different color, say blue, whichwould give the Type 60 Nitinol saw a very distinctive appearance.

The saw blade 415 may be made as shown in FIG. 41 with a cutting edge430 made of Type 60 Nitinol welded to a saw body 435 made of lower costmaterial with a higher modulus, such as titanium. This produces a lowercost saw with a higher modulus. The welding may be laser welding orroller resistance welding that would require little or no touch-upsurface grinding.

The same process can be used to make band saw blades, hand saw bladesand circular saw blades. The band saw blade are made in strips of thinType 60 Nitinol material and cut to length and welded in a loop usinglaser welding. The teeth are tough and abrasion resistant, so they aregood candidates for cutting problem materials such as composites thatquickly dull conventional hardened steel band saw blades.

Polycrystalline cubic boron nitride tooling may be used for machiningthe flat surfaces of the knife blank and the knife edge instead ofgrinding. The cutting depth must be more shallow than for normalmachining, and the feed rate is also slower. Cutting with PCBN toolsgenerate lower cutting forces and removes heat from the workpiece in thechips, so the workpiece remains cool. Although the PCBN is far moreexpensive than grinding wheels and belts, the benefits of its usecompared to grinding are better surface finish, reduction of unwantedheating of the Type 60 Nitinol ground surface, and elimination ofgrinding dust

Obviously, numerous modifications and variations of the preferredembodiments disclosed herein will occur to those skilled in the art inview of this specification. Accordingly, it is to be expresslyunderstood that these modifications and variations, and the equivalentsthereof, are to be embraced within my invention as defined by the spiritand scope of the following claims, wherein I claim:
 1. A cuttinginstrument comprising: a cutting instrument body having a blade with acutting edge; said cutting instrument body made of Type 60 Nitinol; saidcutting instrument body having a hardness greater than about 50 on theRockwell C scale, and said cutting edge heat treated to a hardnessexceeding 57 on the Rockwell C scale for exceptional edge holding; anintegral surface material on said instrument body having properties ofextreme hardness, high electrical resistivity, chemical non-reactivity,slipperyness and a color selected from the group of light gold darkgold, red/purple, light blue, dark blue, silver and grey, said integralsurface material being formed on said instrument body by heating saidcutting instrument body to a temperature at which surfaces of said Type60 Nitinol turns to a desired one of said colors, and allowing saidcutting instrument body to cool slowly.
 2. A cutting instrument,comprising: a cutting instrument body having a blade with a cuttingedge; said cutting instrument body made of Type 60 Nitinol, and heattreated to about 600° C. to 900° C. and allowed to cool slowly to reducebrittleness and notch sensitivity and improve toughness; said cuttinginstrument body having a hardness greater than about 50 on the RockwellC scale, and said cutting edge heat treated to a hardness exceeding 57on the Rockwell C scale for exceptional edge holding.
 3. A cuttinginstrument as defined in claim 2, wherein: said blade is a razor blademade of a strip of thin gauge Type 60 Nitinol sharpened along at leastone longitudinal edge to a sharp edge.
 4. A cutting instrument asdefined in claim 2, wherein: said blade is a flat, elongated saw bladehaving two flat faces and a direction of elongation, and having at leastone cutting edge extending generally parallel to said direction ofelongation; said saw blade having two opposed ends in the direction ofelongation, and having attachment structure adjacent to at least one ofsaid ends to which a handle is attached; said saw blade having at leastone edge portion, including said cutting edge, made of Type 60 Nitinol;a multiplicity of saw teeth along said cutting edge, said saw teethhaving pointed ends pointed generally normal to said direction ofelongation; said saw teeth set to a set position projecting laterallyslightly beyond the planes of said flat faces for cutting a kerf widerthan the thickness of said saw blade; said saw teeth set by heating saidone edge portion to a forming temperature above about 500° C. anddeformed laterally outward to said set position, and held in said setposition while cooling to a temperature below about 400° C.
 5. A cuttinginstrument as defined in claim 2, wherein: said cutting instrument is aknife having a knife body including a knife blade and an integral tangfor mounting a handle; said knife body having a strongback with ahardness greater than about 50 on the Rockwell C scale.
 6. A cuttinginstrument as defined in claim 5, wherein: said knife blade being madeof a blade material that is monolithic Type 60 Nitinol having immunityto corrosion in sea water.
 7. A cutting instrument as defined in claim6, wherein: said blade material has a magnetic permeability at least aslow as about 1.002.
 8. A cutting instrument comprising: a blade having acutting edge having a hardness in excess of 50 on the Rockwell C scale;said blade being made of a monolithic piece of Type 60 Nitinol materialhaving immunity to corrosion in sea water; an integral surface materialon said instrument body having properties of extreme hardness, highelectrical resistivity, chemical non-reactivity, slipperyness and acolor selected from the group of light gold, dark gold, red/purple,light blue, dark blue, silver and gray, said integral surface materialbeing formed on said instrument body by heating said blade to atemperature at which surfaces of said Type 60 Nitinol material turns toa desired one of said colors, and allowing said blade to cool slowly. 9.A cutting instrument, comprising: a blade having a cutting edge having ahardness in excess of 50 on the Rockwell C scale; said blade being madeof a monolithic piece of Type 60 Nitinol material having immunity tocorrosion in sea water, and heat treated to about 600° C. to 900° C. andallowed to cool slowly to reduce brittleness and notch sensitivity andimprove toughness.
 10. A cutting instrument as defined in claim 9,wherein: said blade material has a magnetic permeability at least as lowas about 1.002.
 11. A cutting instrument as defined in claim 9, wherein:said cutting edge is heat treated to a hardness exceeding about 57 onthe Rockwell C scale for exceptional edge holding.
 12. A cuttinginstrument as defined in claim 9, wherein: said blade is a razor blademade of a strip of thin gauge Type 60 Nitinol sharpened along at leastone longitudinal edge to a sharp edge.
 13. A cutting instrument asdefined in claim 9, wherein: said blade is a flat, elongated saw bladehaving two flat faces and a direction of elongation, and having at leastone cutting edge extending generally parallel to said direction ofelongation; said saw blade having two opposed ends in the direction ofelongation, and having attachment structure adjacent to at least one ofsaid ends to which a handle is attached; said saw blade having at leastone edge portion, including said cutting edge, made of Type 60 Nitinol;a multiplicity of saw teeth along said cutting edge, said saw teethhaving pointed ends pointed generally normal to said direction ofelongation; said saw teeth set to a set position projecting laterallyslightly beyond the planes of said flat faces for cutting a kerf widerthan the thickness of said saw blade; said saw teeth set by heating saidone edge portion to a forming temperature above about 500° C. anddeformed laterally outward to said set position, and held in said setposition while cooling to a temperature below about 400° C.
 14. Acutting instrument as defined in claim 9, wherein: said cuttinginstrument is a knife having a knife body including a knife blade and anintegral tang for mounting a handle; said knife body having a strongbackwith a hardness greater than about 50 on the Rockwell C scale.
 15. Acutting instrument as defined in claim 14, wherein: said knife bodybeing made of a monolithic piece of Type 60 Nitinol having immunity tocorrosion in sea water.
 16. A knife, comprising: a knife body having ablade and an integral tang for mounting a handle; said knife body madeof Type 60 Nitinol cut from a plate hot rolled from an ingot of Type 60Nitinol, and heat treated to about 600° C. to 900° C. and allowed tocool slowly to reduce brittleness and notch sensitivity and improvetoughness; said knife body having a strongback with a hardness greaterthan about 50 on the Rockwell C scale, and a cutting edge heat treatedto a hardness exceeding 57 on the Rockwell C scale for exceptional edgeholding.
 17. A knife as defined in claim 16, further comprising: top andbottom blade surfaces ground smooth with grinders having cubic boronnitride abrasive particles to a surface finish of less than about 2microinches.
 18. A knife as defined in claim 17, wherein: said knife isfree of galling, distortion, and micro-cracks, by grinding said top andbottom surfaces at a surface speed of about 5000 to 7000 surface feetper minute with a depth of cut of about 0.002-0.005 inches per pass. 19.A knife as defined in claim 16, further comprising: a tang extension oftitanium welded onto said knife tang and embedded in said handle.
 20. Aknife as defined in claim 16, further comprising: a hollow ground edgeportion on said blade, ground with a belt grinder.
 21. A saw,comprising: a flat, elongated saw blade having two flat faces and adirection of elongation, and having at least one cutting edge extendinggenerally parallel to of said direction of elongation; said saw bladehaving two opposed ends in the direction of elongation, and havingattachment structure adjacent to at least one end to which a handle isattached; said saw blade having at least one edge portion, includingsaid cutting edge, made of Type 60 Nitinol; a multiplicity of saw teethalong said cutting edge, said saw teeth having pointed ends pointedgenerally normal to said direction of elongation; said saw teeth set toa set position projecting laterally slightly beyond the planes of saidflat faces for cutting a kerf wider than the thickness of said sawblade; said saw teeth set by heating said one edge portion to a formingtemperature above about 500° C. and deformed laterally outward to saidset position, and held in said set position while cooling to atemperature below about 400° C.
 22. A saw as defined in claim 21,wherein: said saw blank of Type 60 Nitinol is cut from a sheet ofhot-rolled Type 60 Nitinol having a final direction of rolling, said sawblank being cut from said sheet with said cutting edge oriented parallelto said direction of rolling; whereby said saw teeth extend generallycross-wise to said direction of rolling.
 23. A saw as defined in claim21, wherein: said saw blank is cut from said sheet of Type 60 Nitinolwith a laser cutting apparatus operating at a speed of at least 100inches/minute.
 24. A saw as defined in claim 21, wherein: said formingtemperature is above about 650° C.
 25. A saw as defined in claim 21,wherein: said saw blade has an integral surface material that is veryhard, slippery and colored a color tone selected from the groupconsisting of gold, red/purple, blue and green.
 26. A saw as defined inclaim 21, wherein: said one edge portion, including said cutting edge,made of Type 60 Nitinol is a strip secured along an edge of a saw bodyof a different material.
 27. A saw as defined in claim 26, wherein: saidone edge portion is welded along said edge of said saw body.
 28. Amethod of making a saw blade, comprising: selecting a flat sheet of Type60 Nitinol with planar surfaces on both lateral sides of a thicknessabout the desired thickness of said saw blade; cutting an elongated sawblank out of said sheet, including a series of pointed teeth along onelongitudinal edge; setting selected ones of said teeth to projectlaterally beyond said planes of said lateral sides, said settingincluding heating said blank along said one edge to a temperature aboveabout 500° C., forming said teeth to said set position at a temperatureabove about 500° C., and holding said teeth in said set position whilethey cool to a temperature below about 450° C.; grinding sharp edgesalong at least one side of said teeth; and heat conditioning said bladeto reduce heat induced brittleness and increase toughness, said heatconditioning including heating said saw blade to a temperature aboveabout 450° and allowing said blade to cool slowly to room temperature.29. A method of making a saw blade as defined in claim 28, wherein: saidflat sheet of Type 60 Nitinol is rolled to a thickness between about0.025 inch and about 0.125 inch.
 30. A method of making a saw blade asdefined in claim 28, further comprising: surface grinding said blank toremove surface imperfections in said blank and reduce the thickness ofsaid blank uniformly to said desired thickness with plane surfaces onboth lateral sides of said blank.
 31. A method of making a saw blade asdefined in claim 28, further comprising: grinding cutting edges oninside edges of said set teeth.
 32. A razor, comprising: a razor blademade of a strip of thin gauge Type 60 Nitinol sharpened along at leastone longitudinal edge to a sharp edge.
 33. A razor as defined in claim32, further comprising: attachment structure on said blade for attachingsaid blade to a handle structure by which a user can manipulate saidrazor for shaving.
 34. A razor as defined in claim 33, wherein saidattachment structure includes: holes in said blade through which studsextend for rigidly securing said blade to a cartridge.
 35. A method ofmaking a razor, comprising: selecting a sheet of Type 60 Nitinol hotrolled to a thickness of about 0.015-0.075 inch; slitting said sheetinto a plurality of individual strips of Type 60 Nitinol; attaching saidstrips to a support; and attaching said support to a cartridge.
 36. Amethod of making a razor as defined in claim 35, wherein: said slittingis by gang roller shearing.
 37. A method of making a razor as defined inclaim 35, wherein: said slitting is by laser cutting.
 38. A method ofmaking a razor as defined in claim 35, further comprising: welding saidindividual strips into a long strip which can be coiled in a roll forconvenient handling by automated razor fabrication equipment.